said by TomS_:
In my experience it was the WiMAX networks that tried to do indoor coverage that had issues. At least a couple of Australian providers tried it and failed and blamed the technology.
We on the other hand did fixed outdoor installations only and we had great success with it. We used 3.4 and 3.65GHz bands.
With 3.5Ghz it is difficult to get good indoor coverage. High power and short distance is necessary. Additionaly we see equipment is very sensitve to interference. So it is very difficult to get a performant network without a lot of spectrum. Designing the network for outdoor coverage is much easier.